From<i> in silico</i> design to <i>in vitro </i>validation: Surfactant free synthesis of Oleuropein loaded levan nanoparticles

Polymer-based nanoparticle systems are gaining increasing attention in drug delivery due to their stability, biocompatibility, and controlled release capabilities. Understanding the self-assembly behavior of polysaccharides is crucial for designing effective nanocarriers, yet the conditions governing their organization remain poorly explored. In this study, we employed a combined in silico and in vitro approach to investigate the self-assembly mechanisms of levan and leverage this knowledge to develop a surfactant-free, bioinspired drug delivery system. Molecular simulations revealed that self-assembly is strongly influenced by pH, with alkaline conditions promoting compact, organized structures and acidic conditions leading to disordered arrangements. Guided by these findings, levan nanoparticles were synthesized both with and without the addition of the commonly used non-ionic surfactants Pluronic F-127 and Tween-80 and under optimal conditions, surfactant-free formulations demonstrated high encapsulation efficiency (similar to 80-92 %), enhanced stability, and controlled release of oleuropein (OLE), a bioactive polyphenol with poor gastrointestinal bioavailability. In vitro release studies demonstrated sustained OLE delivery over 24 h, with diffusion-controlled kinetics in intestinal conditions. Antioxidant activity assays confirmed that OLE retained its radical-scavenging properties post-encapsulation. Furthermore, cytocompatibility tests using fibroblast and colon cancer cell lines demonstrated that levan nanoparticles were non-toxic and supported cell viability.